I have a Choate Mark 5 on my 870. It is adjustable for lop.
I prefer a 13" Youth Speedfeed non-pistol grip stock. With a factory length of pull buttstock, my left arm is almost straight. Helps me keep the same stance as I shoot with a handgun and carbine. With my left arm almost locked out, it forced me to almost use a weaver stance.
I’m not a CASer (yet) but this holds true for me, too. My FN SLP is about as good as it gets for me. 
Huge fan of the mesa mounts prefer the AR grip style built bullet proof and not too overly heavy for what you get.
I like a 12-13" LOP I run the Hogue overmold on my 870. I run an 870 with a 18" Tube and i feel that this balances well.
I have tried the black hawk or Knoxx stocks and didnt like them… not sure why but had issues… not with the stock they were all me
GOOD luck
Hey guy’s I bought a Mossy 930spx and want to install a fixed buttstock with a pistol grip. I’ve seen some other 930s with this setup is it factory or is there a an aftermarket stock I can buy.
2nd question: does surefire make a forearm light for the 930spx?
Thanks